Chabazite is the only natural zeolite currently employed commercially to any significant extent. This utility results from unique ion-exchange selectivities and high acid tolerance in adsorptive applications. Most notably, high ion-exchange selectivity towards .sup.137 Cs.sup.+, the largest radioactive component in nuclear reactor waste water streams, results in its employment as a radionuclide scavenger. Secondly, the high acid stability of naturally ocurring chabazite compared to synthetic zeolites makes chabazite the desiccant of choice for commercial use in certain gas streams.
Before any zeolite can be employed in a commercial adsorption or ion-exchange process, powdered material must be formed into macroscopic aggregates so that vapors or liquids may flow through a bed of the material at reasonable throughput and applied pressure. Classical aggregation is achieved by compounding a given zeolite with a binder such as a clay mineral or a `gluing` agent such as a soluble silicate. Unfortunately these binding agents, which may constitute a substantial weight fraction of the finished aggregates, are generally inert with respect to ion-exchange or adsorption, and thereby dilute the desirable properties of the active zeolite component in the moieties. Inert binding agents can also hinder mass transfer of exchangeable ions or adsorbate molecules to active sites. Both of these effects are highly undesirable.
Attempts to overcome the dilution effect of the binders have generally centered on either identification of more effective binders, i.e. those required in lesser amounts, or on the partial or complete conversion of a binding agent to an active phase, sometimes resulting in essentially pure self-bound aggregates with equilibrium ion-exchange and adsorptive properties rivaling those of pure, unbound powders of the same species. See U.S. Pat. No. 4,603,040, Kuznicki et. al.
Extensive ion-exchange and adsorption testing has revealed that unbound sodium chabazite has substantially higher adsorption and ion-exchange capacities than commercial mixed cation chabazite aggregates. The belief that a substantial portion of the capacity is lost due to binder dilution lead to attempts to identify a binder which could be partially or completely converted to chabazite.